1. Field of the Invention
The present invention relates to a focused ion beam apparatus having a gas field ion source.
2. Description of the Related Art
In the related art, liquid metal gallium is employed as an ion source of a focused ion beam apparatus. In recent years, a focused ion beam apparatus employing a gas field ion source which is configured to supply an ion source gas to a fine tip, ionize the ion source gas adsorbed to the tip by a strong electric field formed at an extremity of the tip, and extract an ion beam is developed.
In the ion source using the liquid metal gallium in the related art, an opening angle of the ion beam ejected from the ion source is on the order of 20 degrees. In contrast, in the gas field ion source, since the ion beam is ejected from several atoms at the extremity of the tip, the opening angle of the ion beam is on the order of several degrees.
When using the gas field ion source, since the opening angle of the ion beam is small, accurate adjustment of the angle and the position with respect to an optical axis in an ion beam barrel is necessary in order to extract the ion beam so as to reach a sample surface from the ion source.
The gas field ion source having an adjusting mechanism configured to adjust the direction of the tip by itself is known (see WO2007067328, mainly FIG. 17).
According to the apparatus configured in this manner, even with the gas field ion source whose opening angle of ion beam is small, adjustment of extraction of the ion beam is achieved on the basis of accurate measurement.
However, the adjusting mechanism as described above has a complex structure, and hence the apparatus having the adjustment mechanism suffers from its costliness. It is often difficult with this mechanism to irradiate the ion beam stably, because the tip is subjected to vibrations.